This is a book dictated by the spirit Neio Lúcio to the medium Francisco Cândido Xavier. The discarnate spirit of Carlos, the teen referred to in the title, writes to his brother Dirceu, who is still incarnate. Carlos explains to Dirceu how his soul left his body when it died, and he tells him about his impressions at the beginning of his new life in the spirit realm with his discarnate relatives and new friends. Carlos also affirms the fact that life after death is but the continuation of life in the physical body, and he emphasizes our need to live in accordance with the teachings of Jesus.